This is a renewal application for a Clinical Research Center that was established eight years ago at the Philadelphia Geriatric Center (PGC) and is now a shared venture of the Section on Geriatric Psychiatry at the University of Pennsylvania and PGC. Through this collaboration the CRC has access to the wealth of clinical populations (primary care, specialty services, and residential care) and the investigators of both institutions with their expertise in clinical geriatric psychiatry, geriatric medicine, health services, neuroimaging, psychology and aging, psychopharmacology and sleep and circadian rhythms research. The CRC is an enabling Center whose activities are focused on depression as it occurs most commonly in late life: in association with medical comorbidity. This is an area in which the enabling resources of a Center can make a unique contribution. The Center consists of three Cores and four Laboratories. The Operational Core (Gary Gottlieb, PI) conducts surveys to characterize the Center's patient populations and serves the laboratories through consultation for investigators and assessment, diagnosis, recruitment, and tracking of patients. It is divided into an Assessment, Recruitment and Tracking (ART) Service housed primarily at PGC and two Penn services, the Psychiatric Diagnostic (PDS) and the Geriatric Medicine (GMS) Services. The Biostatistics and Data Management Core (Brian Strom, PI) has responsibilities for consultation on study design, for data management, and for data analysis. A third Core, the Educational Core (Ira Katz, program director), is described in a renewal application for an NRSA training grant that was submitted earlier. The Laboratories are: Geriatric Psychopharmacology (Ira Katz, PI), Neuroimaging (Anand Kumar, PI), Sleep and Circadian Rhythms (Andrew Winokur, PI), and Quality of Life/Health Services Research (Patricia Parmelee, PI). The primary patient populations are: long term care, inpatient rehabilitation, cardiovascular disease, and osteoarthritis; they were chosen for investigation because they support hypothesis-driven research in critical areas related to the interactions between depression and medical illness.